In​ the last decades of the 16th century, Rome attracted visitors much as Moscow would in the 1920s and 1930s. Like Moscow, it was the centre of an international movement that sought to transform the world. Like Moscow, it provided spectacles for tourists and enclaves for foreign recruits, who were often warmly admired but never wholly trusted. And like Moscow, Rome was a Rorschach blot in the shape of a city: visitors found what they were looking for. True believers like the English priest Gregory Martin, who arrived in 1576, came in search of Christian piety. When the Veil of Veronica and other relics were displayed, ordinary Romans were ‘so ravished with devotion’, he wrote, ‘and sodenly touched with sweete compunction, that I was ashamed of mine owne hardnesse and coldnesse’. Montaigne, a more sceptical Catholic who arrived four years later, agreed that the city’s relics touched its citizens to the core. But he also noted that the pope and cardinals tended to talk to one another during sacred ceremonies, and sometimes deliberately broke up rituals with what looked like practical jokes. Unlike Martin, he realised that papal efforts to suppress the city’s courtesans had failed completely. The playwright and pamphleteer Anthony Munday, who visited Rome in 1579, dismissed the relics as ‘rotten bones, which they make the people credite to be the bones of Saintes’. Even the invitation to watch a Jesuit flagellate himself, and then to imitate him, left Munday unexcited. When the Jesuit promised that he ‘shoulde not finde any paine in it, but rather a pleasure’, Munday confessed that he was not yet brave enough to try it, though he hoped he would be. ‘My aunswer,’ Munday recalled, ‘pleased him indifferentlie, so I left him in his Chamber, and went downe, lamenting to see a spectacle of so great follie.’

All of these men, in their different ways, acknowledged a fundamental truth about Rome: the long neglected centre of the Church was transforming itself into the grandest of cities. In the early 15th century, when the papacy returned from its Babylonian captivity in Avignon, Rome was a shadow of its ancient imperial self. Perhaps twenty thousand people lived in a city built for a million. Sheep grazed on the Forum, where the great dramas of the Republic had been staged, and on the hills, where warlords and emperors had built their palaces. The streets were no longer thoroughfares: feuding aristocratic families and professional thieves had turned them into places of carnage and robbery; porticos and stairways projecting from house fronts transformed them into obstacle courses, made even harder to navigate by open sewers, piles of dung and butchers’ refuse. The narrow alleys that led off the main streets, two or three feet wide, were no better: human and animal waste piled up until the walls on either side began to collapse. Undignified little shops housing vendors of holy objects obscured façades and colonnades. The ceremonies staged in the great old basilicas remained impressive – though papal masters of ceremonies, whose knowledge of Roman ritual scripts had been interrupted by the papacy’s exile in Avignon, often found themselves clutching on to one another, terrified that the wrong cleric had censed the pope.

Amid the ruins, a new city slowly rose. Ambitious popes such as Nicholas V in the 1440s and 1450s, known for his wild spending on buildings, books and vestments, and Julius II half a century later, found ways to mark the city as their own. Nicholas fortified the Borgo, the area around Saint Peter’s Basilica, and rebuilt the Trevi fountain, part of an ancient system that still brought water into the city (one of the tasks, and one of the marks, of authority in Rome). Julius planned to drive a long, straight road, the Via Giulia, through the heart of the city, connecting Rome’s river port with its centre and providing a unified space for the administrative offices of the papacy. Though neither succeeded in rebuilding Saint Peter’s, they changed the fabric of Rome, as did the city government, which pressed for cleaner streets and more effective sewers; the cardinals and bankers who built palaces in the centre and across the river in Trastevere; the patrons – including foreign monarchs as well as ambassadors and local grandees – who replaced medieval churches or adorned them with up-to-date façades, sculptures and frescoes; and the popes and religious orders, the Jesuits above all, who founded colleges.

None of the most ambitious plans for urban renovation, whether drawn up by popes or patricians, ever reached completion. Even in the later 16th century, most Roman streets were still unpaved and carpeted with dung dropped by the buffalos that pulled carts and the horses that drew the newly fashionable carriages of the elite. Gregory XIII and Sixtus V both tried to stop the rowdy and unemployed poor from wandering through the streets and squares, ‘groaning and shouting’. Both built hospitals, and Sixtus even planned to turn the Colosseum into a centre for wool manufacture with housing for its workers. But their efforts came to little: in 1600 a report on charity in Rome remarked that the streets were filled with beggars ‘in such great numbers that one is not able to stand or go through the streets if one is not continually surrounded by them’. Yet when Montaigne visited, he had to admit that Rome’s grand public spaces and beautiful streets and palaces far outdid their counterparts in Paris. One of the chief mysteries of late Renaissance Rome is that beauty and order emerged from the chaos and incompetence of planning.

Another visitor, an Irishman of English parentage called Henry Piers, helps us to locate the creative forces in Roman life that made these changes possible. At Easter 1596 he joined the crowds in the Piazza Navona, watching the solemn celebrations inside and outside the church of Saint James of the Spanish. A ‘castle’ had been erected on top of each of the fountains in the piazza. As Piers watched, an angel descended from one of the castles and set fire to an ‘artifitiall divell’. Musical instruments sounded and fireworks exploded. Then the Spanish and Turkish galley fleets appeared between the fountains, and the Turkish fleet was blown up. Perhaps to avoid making the groundlings too happy, a ‘Rounde Compassed thinge representinge the worlde’ first revolved and then went up in flames, to remind them that the world would end in fire. Then the two castles ‘sodenly turned into scorchinge flames, wherewthall a number of great ordinance of many small Pices were shotte of’.

Piers’s city, more than that of other foreign observers, had a future as well as a past. Its stockpiles of relics and ruins were flanked by ingenious devices, some of them new and all of them impressive. Piers marvelled at the Jesuits’ new spiritual technologies. Unlike Gregory Martin, he felt no reservations about describing, in detail, the ways in which a ‘ghostlie Father’ took each Jesuit novice through the Spiritual Exercises, the guide to meditation and choice of vocation drawn up by their founder, Ignatius Loyola. Even more thrilling were the physical marvels of Roman technology: for example, the ‘rare cunninge and arte’ that Sixtus V and his architect Domenico Fontana had deployed to move the obelisk that had stood next to Old Saint Peter’s through the Middle Ages, and re-erect it in front of the enormous new basilica that was slowly taking shape.

Pamela Long has written the first full-scale history of Henry Piers’s Rome. Engineering the Eternal City tells the story of the streets and squares, churches and palaces that astonished, and sometimes disgusted, Martin and Montaigne, Munday and Piers. Long identifies their builders and teases out the complex, tangled forms of papal will, administrative mess and technical know-how that brought them into being. Her task has been neither easy nor simple. The evidence for each segment of the story is scattered: books and manuscripts, prints and maps describing projects, successful and unsuccessful; and documents in Roman archives and libraries, as tricky to navigate as they are rich in material, explaining where the money came from, how decisions were made and how they actually turned out. Many scholars have investigated individual parts of the story, but Long has examined all of this disparate material and forced it to yield a riveting history.

The failures and delays of the most ambitious projects are easy to understand. Rome, Long shows, was a technical nightmare. The water and sewer systems of the imperial capital were for the most part as ruinous as its streets, and natural disasters regularly overwhelmed them. The Tiber overflowed its banks in 1530, 1557, 1567 and 1589. Floods carried away parts of the bridges, destroyed the water mills that ground the city’s grain and filled the streets with sewage. Administrative responsibility for Rome’s infrastructure was divided, and organisations regularly changed both their shapes and their names. The popes assigned particular tasks to committees known as congregations, and headed by cardinals. But nothing lasted. In 1568, for example, Pius V created a Congregation on Streets, Bridges and Fountains, which was reorganised out of existence by Sixtus V twenty years later. Meanwhile the Capitoline Government, established in 1143 to represent the interests of the Roman ‘people’ – that is, the elite of secular society – appointed its own committees, such as the Masters of the Streets, to carry out the same tasks. Courts and jurisdictions, as well as committees, often overlapped and sometimes interfered with one another. When the papacy returned to Rome from Avignon, the papal administration engorged the office of the Masters of the Streets, which eventually obtained wide-ranging powers to confiscate land and buildings and to see to it that streets were paved and cleaned (and which often continued to work, in other capacities, for the Capitoline Government). Drawing on the work of other scholars and her own years of digging in Rome’s bottomless archives, Long sorts out these offices and explains their shifting and deceptive technical vocabulary.

In 1551 Julius III, alarmed by the incidence of disease, imposed a tax on commercial establishments to pay for the cleaning of the streets. He appointed officers to organise the enterprise, including a treasurer and an overseer to maintain accounts and pay workmen, and designated not only the workmen to be hired, but also the equipment they would need. But the money from the first year’s tax was diverted to other needs, then the tax was discontinued. In 1552, Julius didn’t even bother to appoint new Masters of the Street. At times, the Rome that Long has unearthed from the documents looks oddly like Robert Musil’s Kakania.

Yet as Piers understood, many individual projects succeeded, in a distinctively Roman way. In antiquity, aqueducts – gently sloping down to the city from springs and lakes in the Alban hills – had filled the city’s fountains and baths. Regular maintenance was necessary, to repair leaks and scrape off carbon incrustation. Shafts gave access to the underground portions of the conduits. But repairs gradually ceased, and so did the flow of water. By the 15th century, only one aqueduct still functioned: the Acqua Vergine, which brought water from the Salone Springs, east of the city, and other springs all the way to the Trevi fountain. It too was urgently in need of repair.

The Acqua Vergine was anything but easy to fix. Deep underground for much of its length, it turned sharply where it entered the city – a fact that had been lost to view since antiquity. Repairs had to begin with establishing its course, and over the decades Agostino Steuco, a Vatican librarian; Pirro Ligorio, an architect and antiquarian; and Luca Peto, a Roman magistrate, all traced its path through the city. In 1561 Pius IV chose Antonio Trevisi, a military engineer, to do the repairs. Despite extensions and cost overruns, he failed. The Capitoline Council, which headed the city government, tried to take over the job, even though doing so required it to impose taxes. It also failed. At the end of the 1560s Cardinal Montepulciano, one of the two leaders of the Congregation on Streets, Bridges and Fountains and an efficient manager, took over the job, appointing Peto and others as advisers. A bond issue provided the funds, and designers and masons set to work. Despite opposition from the Capitoline Council and complaints from rivals that the terracotta pipes employed for the task ‘caused damage in the same way as a sieve’, by the early 1570s plentiful fresh water flowed, at deliberately low prices, to private houses and nine public fountains in the Campo Marzio.

On the one hand, it’s a grim story. Experts repeated one another’s work while insisting that their colleagues were incompetent. Authorities that could have collaborated instead competed. Meanwhile, thirsty Romans bought their water from the acquaroli who walked the streets, hawking water from barrels borne by donkeys. On the other hand, as Long shows, it’s a dazzling tale of interdisciplinary inquiry, carried out by a strikingly wide variety of investigators. In Rome as elsewhere in this period, architects and engineers, artists and antiquarians were not licensed practitioners of regulated professions but experts who had established their authority by practical work. Some of them had begun life as scholars, some as craftsmen. But their roles in Rome depended on accomplishments, not birth. Ambitious men set out to acquire the skills that their original training had not provided.

Anyone interested in the course of the Acqua Vergine had to read ancient sources – especially the work of Julius Frontinus, a first-century Roman curator aquarum, on the city’s aqueducts. But he also had to read the landscape, following the airshafts, many of them later filled in by farmers, that ancient masons had left to enable repairs across the city. Agostino Steuco, the first expert in the field, was the Vatican librarian, a scholar and standard-bearer for the authority and splendour of the Roman Church. The second, Pirro Ligorio, was an expert of a very different stripe: an artist and architect from Naples and a great expert on Rome’s ruins. Steuco, a library rat, spent months outdoors, following the Acqua Vergine, air shaft by air shaft. Ligorio, who knew Rome’s monuments and cityscapes better than anyone else, trained himself to read texts, especially those available in Italian translation. He mapped the aqueduct, drew its above-ground remains and studied the techniques that its builders had used to make it solid and watertight. The third, Luca Peto, a magistrate, read Frontinus and crept into the underground portions of the aqueduct. Though none of them acknowledged as much, they embraced similar methods and reached the same conclusions.

As Long traces the histories of streets and bridges, maps and images, illustrated with a wealth of vivid woodcuts and engravings, narratives like that of the Acqua Vergine take shape. Together, they tell a new story. The papal city became the home of a distinctive, interdisciplinary culture of knowledge. From the early 15th century, artists like Donatello and Ghiberti and scholars like Leon Battista Alberti abandoned their studies and ateliers to explore the city’s ruins, Christian as well as ancient. Printing gave their successors a way to preserve parts of their work. From the early 16th century, collections of inscriptions and maps and plans of the ancient city and its modern counterpart streamed from the presses. Debate was sharp and constant. Ligorio and Benedetto Egio on the one hand, Bartolomeo Marliani on the other, denounced one another for mislocating the Forum and similar mistakes. Their creativity with insults – they used names from Aristophanes’ Clouds – was as impressive as their erudition.

But disciplinary border-crossing, collaboration and conversation were just as common. Leonardo Bufalini, whose map of the city appeared in 1551, added a self-portrait, complete with surveyors’ and carpenters’ tools. These revealed the humble background as a craftsman from which he had risen to win recognition as an antiquarian. Marliani, whose smaller map of 1544 may have helped to inspire Bufalini, was a scholar of Greek rather than a craftsman. So he enlisted Giovanni Battista Palatino, a famous scribe who had published a manual of calligraphy in 1540, to letter his map. A hospitable and generous man, Marliani liked to entertain fellow antiquaries at his house and to discuss problems with them at the printers’ shops.

Scholars learned from artisans and artisans from scholars, and modest beginnings were no impediment to becoming an oracle on the ancient city or transforming the infrastructure of the modern one. Adapting a phrase from Peter Galison, an influential historian of modern science, Long calls late Renaissance Rome a ‘trading zone’: one of the many places, like courts and monasteries, printers’ shops and artists’ ateliers, where men of the book could try out work that dirtied their hands, and men of what Dürer called the ‘learned hand’ (docta manus) could learn to interpret texts. Roman society – everyone agreed – was unusual in many ways: for every hundred men there were only seventy women. But nothing did more to set Rome apart from other communities than this culture of conversation and exchange. Perhaps in this light, Rome looks less like Stalin’s Moscow than like La Guardia’s New York.

For all his admiration for the white heat of Roman technology, even Piers was surprised by the ease with which some Romans moved from one social rank to another. He greatly admired Saint Peter’s Square, the vast piazza in front of the new basilica, where as many as a thousand coaches might appear on feast days, and the ‘aguillio or piramides of a mightie heighte’ that dominated it: the Vatican obelisk. Piers knew that ‘this piramedes was sett upe with suche rare cunninge and arte as was wonderfull unto them wch sawe the same.’ But he was still surprised to learn that Fontana ‘was knighted for the same, wch is a degree unto the wch artificers are rarely preferred unto’.

In fact, Fontana’s transportation of the Vatican obelisk was the culmination of all these late Renaissance projects. Like them, it was born from conversation. For more than a century, popes and builders had discussed the possibility of moving the immense granite shaft. Michelangelo had refused to try it: ‘And what,’ he asked, ‘if it breaks?’ Architects, bankers and others devised machines which, they claimed, could do the job. Finally, when Felice Peretti was named Pope Sixtus V, Fontana – who had begun doing masonry and stucco work, but had become Peretti’s architect – received the commission. He gathered materials, taking full advantage of multiple concessions: hundreds of feet of rope, dozens of pulleys, immense oak beams and shafts. In late April 1586, Fontana’s workers encased the obelisk in an enormous wooden castello – a combination scaffold and crane. He held rehearsals, masses were said, and houses were demolished to make room. On 30 April, the first trumpet blew. Forty capstans turned by horses and controlled by teams of men pulled the obelisk from its ancient base. At first, ropes broke, so Fontana changed his procedure. Then all went smoothly, as thousands watched, awed for once into silence. On 27 September, the obelisk was raised again in front of the new Saint Peter’s. A bishop climbed a ladder to exorcise any Egyptian demons that might still inhabit the shaft. The Swiss guards fired their cannon and the garrison of the Castel Sant’Angelo let off their mortars. ‘Never before,’ Long writes, ‘had an engineering project also served as such an elaborate urban spectacle and at the same time a deeply solemn occasion for a religious rite.’ This seems to bring us around again to Moscow, where two thousand metro workers offered a choral performance to celebrate the opening of the first subway line, and thousands of copies of Songs of the Joyous Metro Conquerors were distributed.

This story has been told before, by Fontana himself and many others. But Long retells it with her customary precision and sense of drama, and adds granular details from the printed and archival sources that no other modern scholar has noticed. She makes clear that Fontana, like all of his predecessors, was fascinated by every detail he could chase up about the engineering techniques of the ancient Romans and eager to find useful contemporary ideas and techniques wherever he could – sometimes in the proposals of his rivals. She traces the sometimes bumpy path of his later career, which saw him repair and move three further obelisks and renovate the columns of Trajan and Marcus Aurelius. He turned these ancient, pagan objects into markers that Christian pilgrims could steer by as they visited the Roman basilicas. The course of technological innovation did not run wholly smooth. After Sixtus died, Fontana was accused of skimming funds and had to retire to Naples, where he again became a great success. Yet he and the great techno-events he orchestrated were products of the 16th-century Roman world of debate and conversation, scholarship and technology – the Rome in which the foundations of the Baroque were laid.